Acceptance
Mirror Image Rule & the Battle of the Forms
1. Mirror Image Rule
 The
rule requires that an offeree respond to an
offer with an acceptance that is definite and
unconditional, and that matches the terms of the
offer exactly and unequivocally.
 Most common-law and civil-law countries follow
the mirror image rule. Under these laws, it is
unlikely for an acceptance containing different or
additional terms to become effective. Such
acceptance is usually considered a counteroffer and
thus a rejection of the original offer.
2. The Battle of the Forms
 As
the mirror image rule requires that an
acceptance be unconditional, both parties, buyer
and seller, have to negotiate back and forth through
standard business forms. The mirror image rule is
the source of the battle of the forms.
offer
 The
counteroffer
counteroffer
…
“last shot” principle:
The form sent last in time will prevail others as the
contract.
3. Modification to Mirror Image Rule
Modification under UCC
 Modification under the CISG----Art. 19
 Modification under China’s contract law---Art.30, 31

Modification
under UCC
A. In the United States the mirror image
rule has been changed by statute (the
UCC) to deal with modern business
practices.-- UCC 2-207
(1) A written confirmation with
additional or different terms operates as
an acceptance unless…
(It breaks the mirror image rule.)
(2) Between merchants, an acceptance by a
A.
B.
C.
confirmation that contains new terms
will produce a contract and new terms
become a part of contract unless:
The buyer (the offeror) expressly
limits …
The new terms materially alter…
The buyer notifies the seller of an
objection to the new terms
B. How to deal with the additional or different
terms
A. To become a part of the contract
The contract is concluded between merchants,
containing those additional or different terms
which only reflects minor differences (related to
usual and customary usage in trade).
B. Not to become a part of the contract
The contract would arise without the new terms if
the new terms reflect major differences ( material
alteration---- that is not commonly accepted in the
trade and that would result in surprise hardship).
Modification under the CISG----Art. 19
1. The CISG compromises between the mirror
image rule set out by the common and civil
law and the UCC. Under the CISG:

(1) the acceptance containing the new terms that do
not materially alter the terms of the offer becomes
a part of the contract.---- close to the UCC
(2) The purported acceptance containing the new
terms that do materially alter the terms of the
offer would constitute a rejection of the offer and
a counteroffer.---- close to the mirror image rule

1. The CISG compromises between the
mirror image rule set out by the common
and civil law and the UCC. Under the CISG:
(1) the acceptance containing the new terms that do
not materially alter the terms of the offer becomes
a part of the contract.---- close to the UCC
(2) The purported acceptance containing the new
terms that do materially alter the terms of the
offer would constitute a rejection of the offer and
a counteroffer.---- close to the mirror image rule
2. Unlike the UCC, the CISG goes further
to define “material alteration” :
The key elements that will materially
alter a contract: price, payment, quality
and quantity of the goods, place and time
of delivery, extent of one party’s liability
to the other or the settlement of disputes

China’s contract law---- Art.30, 31
第三十条 承诺的内容应当与要约的内容一致。
受要约人对要约的内容作出实质性变更的，
为新要约。 有关合同标的，数量，质量，价
款或者报酬，履行期限，履行地点和方式，违
约责任和解决争议方法等的变更， 是对要约
内容的实质性变更。
第三十一条 承诺对要约内容作出非实质性变更
的，除要约人及时表示反对或要约 表明承诺
不得对要约的内容作出任何变更的以外，该承
诺有效，合同的内容以承诺的内容为准。
 China’s
contract law---- Art.30, 31
Article 30 The contents of an acceptance shall
comply with those of the offer. If the offeree
substantially modifies the contents of the offer, it
shall constitutes a new offer. The modification
relating to the contract object, quality, quatity,
price or renumeration, time or place or method of
performance, liabilities for breach of contract and
the settlement of disputes, etc., shall constitute the
substantial modification of an offer.
Article 31 If the acceptance does not
substantially modifies the contents of the
offer, it shall be effective, and the
contents of the contract shall be subject
to those of the acceptance, except as
rejected promptly by the offeror or
indicated in the offer that an acceptance
may not modify the offer at all.
Conclusion
Mirror image rule is adopted by most
countries of the world. In order to pursue
the flexibility of contracting, the UCC,
the CISG and China’s contract law
modify this rule to some extent. The
CISG is close to the UCC somewhat, but
it has more specific provisions. China’s
contract law is similar to the CISG.
